Permission's been refused for a seven floor office block off Pearse Street in case it could affect the Dart Underground.
That's despite fears the rail project won't end up going ahead.
The owners of the site on Sandwith Street will now face a bill next year for €100,000 euro for sitting on land that's not being developed.
An Bord Pleanála says the building can't go ahead because it could significantly compromise the proposed Dart Underground.
The rail project, which would link the main train stations, was included in Transport Strategy for the Greater Dublin Area but there's been no commitment to build it under the government's Ireland 2040 spending plan.